Rectifying discharge tube



Sept. 26, 1933. P. w. DOBBEN ET AL 1,928,370

RECTIFYING DISCHARGE TUBE Filed April 19. 1927 Patented Sept. 26, 1933 UNITED STATES PATENT OFFICE BECTIFYING DISCHARGE TUBE Gloellampeniabrieken,

Eindhoven, Net h er lands, a company of the Kingdom of the Netherlands Application April 19, 1927, Serial No. 185,044, and in the Netherlands May 20, 1926 3Claims.

The invention relates to rectifying discharge tubes comprising anodes consisting of a metal core which is superficially coated with carbon. The core may consist of tungsten; in that case it may be arranged in the discharge tube in the shape of a helix and may be surrounded by a carbon cylinder.

The great advantage arising from the use of carbon anodes in rectfying discharge tubes is, as known, due to the high inverse voltage obtained when such anodes are used. The term inverse voltage must be understood to mean the voltage at which the current starts to pass in the direction from the cathode to the anode. When using carbon anodes, this inverse voltage is considerably higher than when metal anodes are used. Carbon anodes have the disadvantage that they cannot easily be deprived of occluded gases. The invention has for its object to secure the high inverse voltage which favorably distinguishes carbon anodes from the metal anodes, and at the same time to retain the easy deprivation of occluded gases characteristic of metal anodes.

The anode of a rectifying discharge tube according to the invention consists of a metal core coated with a graphite solution which may or may not contain a binding agent; the anode can be deprived of occluded gases in any known manner, for example by arranging it in a high frequency field, in which case the anode is heated by the Foucault currents produced in it by the inducing field. With high frequency deprivation of occluded gases the volatile components are expelled and the carbon layer is baked together so as to form a thin coherent coating. The anode may also consist of a metal helix surrounded by a carbon cylinder. Such an anode can be deprived of occluded gases for example by galvanically heating the said helix.

It is also possible to use an anode consisting of a. metal core (for example, a tungsten helix) on which a graphite solution is applied. Such an anode can be deprived of occluded gases by heating the core to incandescence in vacuum, a small coherent carbon block with a metal core being thus produced.

The invention will be more clearly understood upon reference to the accompanying drawing illustrating a preferred embodiment thereof.

In the drawing,

Fig. 1 is a diagram representing a circuit arrangement comprising a rectifying tube, and

Fig. 2 is a sectional view of an electrode according to the invention.

InIdgJarectiflerisshowncompi-isingan anode 1 constructed in accordance with the invention and a cathode 2. In circuit with the rectifier is a battery 3 to be charged. A transformer for energizing the circuit comprises the primary and secondary windings 4 and 5, respectively. The provision of an anode 1 consisting of a metal core coated with carbon has the advantage that the inverse voltage, that is, the voltage at which the current would pass in the direction from the cathode 2 to the anode 1 and at which the battery would be discharged, is increased.

As shown in Fig. 2, a preferred form of anode comprises a metal wire 5, for example of tungsten, wound in the form of a helix closely spaced from the central portion 6. The wire 5 is surrounded by a carbon cylinder 7. The upper end of thehelix 5 is connected to the conductor 6 while the lower end is secured to a conductor 9, so that the electrode is supported upon the conductors 8 and 9, these conductors also serving to conduct current to the anode. After the electrodes are mounted in the tube, the latter is connected to a pump. A voltage is then applied to the conductors 8 and 9 whereby the helix 5 is galvanically heated to incandescence during the evacuation of the tube. In this manner the carbon cylinder '1 is readily freed of occluded gases.

What we claim is:

1. An anode for an electric discharge tube comprising a core consisting of a helically-wound metal wire and a hollow carbon body placed over said core and in direct heat-conducting and electrically-conducting relation with said core.

2. An anode for an electrical discharge tube comprising a core consisting of a helically-wound metal wire and a hollow carbon body surrounding said core and in direct heat-conducting and electrically-conducting relation therewith, said core also forming the support for the anode.

3. An electric discharge tube including an incandescent cathode and an anode having a core with a surface of carbon, said core comprising a metallic member of helical form adapted to heat said surface, said surface comprising a hollow cylinder of carbon positioned directly on said core. 

